The present invention relates to a thermoplastic resin composition superior in heat resistance, impact resistance, mar resistance, water resistance and surface gloss.
Crystalline polypropylenes are superior in mechanical properties and moldability and used in wide applications, but are not satisfactory in heat resistance and impact resistance when used in industrial parts. It has conventionally been conducted to add an inorganic filler to a crystalline polypropylene to improve the heat resistance of the latter, or to add an ethylene-.alpha.-olefin copolymer rubber or a polyethylene to a crystalline polypropylene to improve the impact resistance of the latter; however, the addition of an inorganic filler significantly reduces the impact resistance of polypropylene and the addition of an ethylene-.alpha.-olefin copolymer rubber or a polyethylene reduces the rigidity, heat resistance and oil resistance of polypropylene. Even the combined addition of an inorganic filler and an ethylene-.alpha.-olefin copolymer rubber or a polyethylene to a polypropylene does not give an effect more than the sum of addition effects of respective additives, and accordingly provides no sufficient method for improvement of polypropylene in heat resistance and impact resistance.
Meanwhile, there was made an attempt of adding a polyamide to a polypropylene to improve the heat resistance, oil resistance, etc. of polypropylene without reducing the impact resistance of polypropylene. However, since there is no compatibility between polypropylene and polyamide, they cause delamination and no desired material can be obtained when they are melt mixed as they are. Hence, there was used, in place of a polypropylene, a modified polypropylene obtained by grafting a polypropylene with an unsatuated carboxylic acid or a derivative of an unsaturated carboxylic acid (Japanese Patent Publication No. 30945/1970). This approach makes a polypropylene and a polyamide to be compatible with each other and can improve the heat resistance of polypropylene without reducing the impact resistance of polypropylene.
However, even in the above improvement of polypropylene by addition of polyamide, the improvement effect is not satisfactory as long as there is used, as the polyamide, an ordinary polyamide such as nylon-6, nylon-6,6, nylon-12 or the like. Recently there has been made a proposal of adding an aromatic polyamide and a glass fiber to a polypropylene to obtain a material of high strength and low water absorbability [Japanese Patent Application Kokai (Laid-Open) No. 203654/1985]. This proposal if not sufficient when viewed from the improvement of polypropylene in both heat resistance and impact resistance. In order to significantly improve the heat resistance and impact resistance of polypropylene by addition of polyamide thereto, the dispersibility of polyamide particles in polypropylene and the cohesivenenss among polyamide particles are very important. The improvement of polyamide particles in these properties has been necessary.